Exhaust silencing device

ABSTRACT

An exhaust silencing device connected to an exhaust system of an engine is provided in which two outlet pipes that have at an upstream end thereof an opening portion opening within the silencer main body and that discharge exhaust gas within the silencer main body to an outside thereof are disposed within the silencer main body along a bottom thereof so that the distances thereof from the lowest part of the bottom are substantially equal, and the opening portion of one outlet pipe is directed further toward the bottom of the silencer main body than is the opening portion of the other outlet pipe. Such exhaust silencing device efficiently discharges to the outside the condensed water building up within the silencer main body so as not to impair an effect in reducing exhaust resistance by providing two outlet pipes that guide the exhaust gas to the outside.

TECHNICAL FIELD

The present invention relates to an exhaust silencing device connectedto an exhaust system of an engine for a vehicle, etc. and, inparticular, to an exhaust silencing device in which an effect inreducing exhaust resistance by providing two outlet pipes within asilencer main body is not impaired by build-up of condensed water.

BACKGROUND ART

Conventionally, an arrangement in which for the purpose of increasingthe flow rate of exhaust gas of a silencer and reducing the exhaustresistance, two outlet pipes (dual type) for exhaust gas to flow areprovided is already known; for example, an exhaust silencing devicedisclosed in Patent Document 1 below includes a silencer main body(silencer), an inlet pipe (exhaust pipe) 2 that has at the downstreamend an opening portion opening within the silencer main body and thatguides exhaust gas from an engine to the interior of the silencer mainbody, and two outlet pipes, that is, a short outlet pipe (tailpipe) 11and long outlet pipe (tailpipe) 12 that have at the upstream end anopening portion opening within the silencer main body and that dischargethe exhaust gas within the silencer main body to the outside of thesilencer main body, an opening portion 12 a of the long outlet pipe 12being positioned above an opening portion 11 a of the short outlet pipe11, and condensed water that builds up at the bottom of the silenceraccompanying the exhaust gas being cooled is discharged outside mainlyvia the short outlet pipe, thereby reducing the flow of condensed waterinto the long outlet pipe.

In the above arrangement of Patent Document 1, if the amount ofcondensed water within the long outlet pipe increased, since there is apossibility that the output of the engine would decrease, the silencingeffect would decrease, and the outlet pipe would be blocked due tofreezing of condensed water in winter, condensed water flowing into thelong outlet pipe has to be reduced.

RELATED ART DOCUMENTS Patent Document

-   Patent Document 1: Japanese Utility Model Registration Publication    No. 3-6808

SUMMARY OF INVENTION Problems to be Solved by the Invention

When the length of the outlet pipe is not so long that the abovepossibility will arise, it is not necessary to intentionally reducecondensed water flowing into the long outlet pipe. When the purpose ofproviding two outlet pipes is to increase the passage cross-sectionalareas of the outlet pipe to thus increase the flow rate of exhaust gasand reduce the exhaust resistance, the flow velocity of exhaust gaspassing through the outlet pipe decreases due to the increased passagecross-sectional area, as a result the power of the outlet pipe to suckup condensed water decreases, and condensed water easily builds up atthe bottom of the silencer; it is therefore desirable for the design tobe such that condensed water is discharged as quickly as possible fromthe two outlet pipes.

The present invention has been accomplished in light of suchcircumstances, and it is an object thereof to provide a novel exhaustsilencing device in which an effect in reducing exhaust resistance byproviding two outlet pipes can reliably be prevented from being impairedby condensed water building up within the outlet pipes.

Means for Solving the Problems

In order to solve the above problems, according to a first aspect of thepresent invention, there is provided an exhaust silencing devicecomprising a silencer main body, an inlet pipe that has at a downstreamend thereof an opening portion opening within the silencer main body andthat guides exhaust gas from an engine to the silencer main body, andtwo outlet pipes that have at an upstream end thereof an opening portionopening within the silencer main body and that discharge exhaust gaswithin the silencer main body to an outside of the silencer main body,

characterized in that the two outlet pipes are disposed within thesilencer main body along a bottom of the silencer main body so that thedistances thereof from the lowest part of the bottom are substantiallyequal, and the opening portion of one of the outlet pipes is directedfurther toward the bottom of the silencer main body than is the openingportion of the other outlet pipe.

In order to solve the above problems, according to a second aspect ofthe present invention, in addition to the first aspect, the silencermain body is inclined upwardly from an upstream side of the silencermain body toward a downstream side of the silencer main body in adirection of flow of exhaust gas, the opening portions of the one andother outlet pipes are on the upstream side within the silencer mainbody, and the opening portion of the one outlet pipe is inclineddownwardly from the upstream side toward the downstream side.

In order to solve the above problems, according to a third aspect of thepresent invention, in addition to the first aspect, the two outlet pipesare formed into an S-shape and are disposed at opposite sides in alongitudinal direction within the silencer main body, upstream-sideoutlet pipes of these outlet pipes are disposed along the bottom of thesilencer main body so that the distances thereof from the lowest part ofthe bottom are substantially equal, and the opening portions formed atthe upstream end of the one and other outlet pipes are disposed in acentral part in the longitudinal direction of the silencer main body.

Effects of the Invention

In accordance with the first aspect of the present invention, when theamount of condensed water building up at the bottom of the silencer mainbody is small, condensed water is efficiently discharged to the outsideof the silencer main body via the one outlet pipe. Furthermore, when theamount of condensed water building up increases, the water level rises,and the amount of condensed water discharged from the one outlet pipedecreases, since the ability of the other outlet pipe to dischargecondensed water improves outstandingly, a state in which there is a highwater level is promptly eliminated. Therefore, it is possible toreliably prevent the effect in reducing exhaust resistance by providingtwo outlet pipes from being impaired by condensed water building up.

Furthermore, in accordance with the second aspect of the presentinvention, a small amount of condensed water building up at the bottomof the silencer main body is promptly collected on the upstream side ofthe silencer main body and quickly and efficiency discharged with littleresistance via one of the outlet pipes that has its opening portioninclined downwardly from the upstream side to the downstream side.

Moreover, in accordance with the third aspect of the present invention,since condensed water building up within the silencer main body isdischarged from the central part in the longitudinal direction of thesilencer main body to the outside via one end or the other end in thelongitudinal direction, even if the silencer main body is long andnarrow, condensed water building up there can be discharged quickly, andit is possible to more reliably prevent the effect in reducing exhaustresistance by providing two outlet pipes from been impaired by condensedwater building up.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an exhaust system equipped with the exhaustsilencing device of the present invention. (first embodiment)

FIG. 2 is an enlarged sectional view along line 2-2 in FIG. 1. (firstembodiment)

FIG. 3 is a sectional view along line 3-3 in FIG. 2. (first embodiment)

FIG. 4 is a sectional view along line 4-4 in FIG. 3. (first embodiment)

FIG. 5 is a diagram showing an exhaust system equipped with the exhaustsilencing device of the present invention. (second embodiment)

FIG. 6 is an enlarged sectional view along line 6-6 in FIG. 5. (secondembodiment)

FIG. 7 is a sectional view along line 7-7 in FIG. 6. (second embodiment)

FIG. 8 is an enlarged sectional view along line 8-8 in FIG. 6. (secondembodiment)

FIG. 9 is an enlarged sectional view along line 9-9 in FIG. 6. (secondembodiment)

FIG. 10 is a transparent view from arrow 10 in FIG. 5. (secondembodiment)

FIG. 11 is an enlarged partial view from arrow 11 in FIG. 10. (secondembodiment)

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

-   1; 101 Silencer main body-   10; 110 Inlet pipe-   11; 111 One outlet pipe-   11 o; 111 o Opening portion-   111 u Upstream-side outlet pipe-   12; 112 Other outlet pipe-   12 o; 112 o Opening portion-   112 u Upstream-side outlet pipe-   E Engine

MODES FOR CARRYING OUT THE INVENTION

Modes for carrying out the present invention are specifically explainedbelow by way of embodiments of the present invention shown in theattached drawings.

In first and second embodiments below, front and rear, left and right,and up and down are with respect to the direction of forward travel ofan automobile equipped with an exhaust system.

Embodiment 1

A first embodiment of the present invention is now explained byreference to FIGS. 1 to 4.

This first embodiment is a case in which the exhaust silencing device ofthe present invention is implemented in a silencer that is mountedlengthwise (disposed in the fore-and-aft direction) in an exhaust systeminstalled in an automobile.

In FIG. 1, an exhaust pipe Pe in an exhaust system Ex of a six-cylinderengine E for an automobile has connected in series thereto, in orderfrom the upstream side to the downstream side, a catalyst CA, auxiliarysilencers (prechambers) MA and MR, and a main silencer MM. Exhaust gasdischarged from the six-cylinder engine E installed on a vehicle body ofthe automobile is passed through the catalyst CA to remove harmfulcomponents such as HC, CO, and NOx, then subjected to auxiliarysilencing while flowing through the auxiliary silencers MA and MR,further subjected to main silencing while flowing through the mainsilencer MM, and discharged to the atmosphere.

The arrangement of the main silencer MM equipped with the exhaustsilencing device related to the present invention is explained in detailbelow by reference to FIGS. 2 to 4.

This main silencer MM is mounted lengthwise (its longitudinal directionbeing in the fore-and-aft direction) so as to be inclined upwardly fromthe upstream side of the main silencer MM in the direction of flow ofexhaust gas toward the downstream side of the main silencer MM. Asilencer main body 1 forming its outer shell is formed from an ellipticcylinder body part 2 and front and rear end plates 3 and 4 closing frontand rear open ends of the body part 2, outer peripheral edges of thefront and rear end plates 3 and 4 being fixed by swaging to outerperipheral faces at front and rear ends of the body part 2 along theentire periphery. A separator 5 for partitioning expansion chamberswithin the silencer main body 1 in the longitudinal direction isprovided in an intermediate part in the longitudinal direction of thesilencer main body 1. This separator 5 is provided with a communicationpipe 6, which provides communication between front and rear expansionchambers partitioned by the separator 5. Furthermore, a water throughhole h opens at the lower end of the separator 5.

Supported in an upper part of a front half of the silencer main body 1is an inlet pipe 10 extending through the expansion chamber in thelongitudinal direction. The front end (the upstream end) of this inletpipe 10 is supported on the front end plate 3 so as to extendtherethrough, communicates with the exhaust pipe Pe, and is welded tothe front end plate 3 together with the exhaust pipe Pe. The downstreamend (rear end) of the inlet pipe 10 extends through the separator 5 andis welded thereto, and its downstream end opens in the interior of theexpansion chamber. This inlet pipe 10 guides exhaust gas from the engineE to the expansion chamber within the silencer main body 1.

Furthermore, arranged side by side in the left-and-right directionwithin the silencer main body 1 are two outlet pipes, that is, oneoutlet pipe 11 and another outlet pipe 12, extending in the longitudinaldirection in the interior of the expansion chamber. The one and otheroutlet pipes 11 and 12 have their intermediate parts supported on theseparator 5 so as to extend therethrough and their downstream ends (rearends) connected, via connecting pipes 15 and 16, to tailpipes 13 and 14extending through the rear end plate 4 and opening to the outside.

The upstream ends (front ends) of the one and other outlet pipes 11 and12 have opening portions 11 o and 12 o opening in a front part of theinterior of the expansion chamber of the silencer main body 1 and guideto the outside exhaust gas that has flowed into the silencer main body 1and has been silenced by the expansion chamber.

As shown in FIGS. 2 and 3, the one and other outlet pipes 11 and 12 aredisposed along the bottom of the silencer main body 1 within thesilencer main body 1 so that the distances thereof from the lowest partof the bottom are substantially equal. The upstream end (front end) ofthe one outlet pipe 11 is downwardly curved, its opening portion 11 o isinclined downwardly from the upstream side of the silencer main body 1toward the downstream side (from the front side to the rear side) and isdirected more toward the bottom of the silencer main body 1 than is theopening portion 12 o of the other outlet pipe 12. The opening portion 12o of the other outlet pipe 12 is directed in the longitudinal directionof the silencer main body 1 (direction substantially parallel to thebottom of the silencer main body 1).

The operation of the first embodiment is now explained.

Exhaust gas generated by operation of the engine E is guided from theexhaust pipe Pe to the expansion chamber through the inlet pipe 10.Exhaust gas that has flowed into the expansion chamber flows in anindirect route from the rear part of the expansion chamber to the frontpart of the expansion chamber via the communication pipe 6 while beingsilenced. The silenced exhaust gas within the expansion chamber isdivided into two, that is, into the one and other outlet pipes 11 and12, via the opening portions 11 o and 12 o of the pipes 11 and 12 anddischarged to the outside via the tailpipes 13 and 14. The flowresistance of the exhaust gas is reduced due to the exhaust gas beingdivided and flowing through the one and other outlet pipes 11 and 12.

When the operation of the engine E is stopped and the main silencer MMis cooled, high temperature exhaust gas flowing there is also cooled;moisture contained in the exhaust gas condenses and, as shown in FIGS. 2and 3, becomes condensed water that builds up within the silencer mainbody 1.

The exhaust silencing device of the first embodiment discharges thecondensed water to the outside via the following process.

[When Condensed Water is at Low Level]

As shown by the solid lines in FIGS. 2 and 3, when the amount ofcondensed water building up at the bottom of the silencer main body 1 issmall and the water level thereof is low, since the opening portion 110of the one outlet pipe 11 is directed toward the bottom of the silencermain body 1, the condensed water is efficiently sucked up through theopening portion 11 o of the one outlet pipe 11 and discharged to theoutside of the silencer main body 1 through the outlet pipe 11.

Furthermore, as shown in FIG. 2, the silencer main body 1 is inclinedupwardly from the upstream side (exhaust pipe Pe side) of the silencermain body 1 toward the downstream side (tailpipes 13 and 14 side) of thesilencer main body 1 in the direction of flow of the exhaust gas, asmall amount of condensed water collects on the upstream side (frontpart) of the silencer main body 1, the upstream ends of the one andother outlet pipes 11 and 12 are on the upstream side (front part) ofthe silencer main body 1, the upstream end of the one outlet pipe 11 isdownwardly curved, and its opening portion 11 o is inclined downwardlyfrom the upstream side of the silencer main body 1 toward the downstreamside of the silencer main body 1 in the direction of flow of exhaustgas, therefore making it possible to promptly and efficiency dischargecondensed water collected at the bottom on the upstream side (frontpart) of the silencer main body 1 through the one outlet pipe 11.

[When Condensed Water is at High Level]

When the amount of condensed water building up increases and the waterlevel of condensed water increases from the above state as shown by thedouble dotted broken lines in FIGS. 2 and 3, since the opening portion110 of the one outlet pipe 11 is directed toward the bottom of thesilencer main body 1, the actual opening area of the opening portion 110into which exhaust gas flows decreases greatly due to the increase inthe water level, the amount of exhaust gas flowing through the oneoutlet pipe 11 decreases, and the amount of condensed water dischargedfrom the one outlet pipe 11 also decreases accompanying this. In thisprocess, since the extent to which the opening portion 12 o of the otheroutlet pipe 12 is directed toward the bottom of the silencer main body 1is small or none, the actual opening area of the opening portion 12 ointo which exhaust gas flows does not decrease a lot even when the waterlevel of condensed water increases, the amount of exhaust gas flowingthrough the other outlet pipe 12 increases by an amount corresponding tothe decrease in the amount of exhaust gas flowing through the one outletpipe 11, and the flow velocity of the exhaust gas flowing through theother outlet pipe 12 increases. This enhances the suction power of theother outlet pipe 12 to suck up condensed water, a large amount ofcondensed water is sucked into the other outlet pipe 12 and dischargedto the outside of the silencer main body 1, and the water level ofcondensed water building up at the bottom of the silencer main body 1decreases again to the above low level.

Embodiment 2

A second embodiment of the present invention is now explained byreference to FIGS. 5 to 11.

This second embodiment is a case in which the exhaust silencing deviceof the present invention is implemented in a main silencer MM that ishorizontally transversely mounted (horizontally disposed in theleft-and-right direction) in an exhaust system Ex installed in anautomobile.

In FIG. 5, an exhaust pipe Pe in the exhaust system Ex of a six-cylinderengine E for an automobile has connected in series thereto, in orderfrom the upstream side to the downstream side, a catalyst CA, auxiliarysilencers (prechambers) MA and MR, and a main silencer MM. Exhaust gasdischarged from the six-cylinder engine E installed on a vehicle body ofthe automobile is passed through the catalyst CA to remove harmfulcomponents such as HC, CO, and NOx, then subjected to auxiliarysilencing while flowing through the auxiliary silencers MA and MR,further subjected to main silencing while flowing through the mainsilencer MM, and discharged to the atmosphere.

The arrangement of the main silencer MM equipped with the exhaustsilencing device related to the present invention is explained in detailbelow by reference to FIGS. 6 to 11.

This main silencer MM is disposed so as to be substantially horizontalin the left-and-right direction (longitudinal direction) and inclinedslightly downwardly to the front in the fore-and-aft direction (widthdirection) (see FIGS. 8 and 9). Therefore, condensed water, describedlater, that builds up within the main silencer MM is collected towardthe front in the fore-and-aft direction.

A silencer main body 101 forming the outer shell of the main silencer MMis formed from an elliptical body part 102 and left and right end plates103 and 104 that close left and right open ends of the body part 102.Outer peripheral edges of the front and rear end plates 103 and 104 arefixed by swaging to outer peripheral faces of the front and rear ends ofthe body part 102 along the entire periphery. Expansion chambers formedwithin the silencer main body 101 are partitioned in the longitudinaldirection by means of four separators 105, 106, 107, and 108, and amongthem the two separators 106 and 107 close to the middle of the silencermain body 101 are provided with a large number of small holes (punchedholes) 120 in order to reduce the sound of the flow of exhaust gas. Thetwo separators 105 and 108 close to the outside are provided with largeholes 121 in order to ease the flow of exhaust gas (see FIG. 10). Inthis way, the expansion chambers are provided with the separators 105 to108, but since exhaust gas flows through the large number of small holes120 provided in the separators 106 and 107 and the large holes 121provided in the separators 105 and 108, the expansion chambers withinthe silencer main body 101 function as substantially one expansionchamber. Furthermore, a water through hole h is opened in each of thelower ends of the plurality of separators 105, 106, 107, and 108.

An exhaust gas introduction pipe 118 connect to the exhaust pipe Pecommunicating with the engine E extends through the right end plate 104from one end in the longitudinal direction of the silencer main body101, and the downstream end thereof is supported on the right end plate104 and communicatingly connected to an inlet pipe 110 within theexpansion chamber.

The inlet pipe 110, which extends in the longitudinal direction withinthe expansion chamber, is formed into a straight line from anupstream-side inlet pipe 110 u and downstream-side inlet pipe 110 d thatare communicatingly connected to each other across a slight gap d in anintermediate part thereof. The upstream-side inlet pipe 110 u issupported on the separators 107 and 108 so as to extend therethrough andhas in its upstream part a large number of small holes (punched holes)122 opening between the right end plate 104 and the separator 108.Furthermore, the downstream-side inlet pipe 110 d is supported on theseparators 105 and 106 so as to extend therethrough and has itsdownstream end opening within the expansion chamber between theseparator 105 and the left end plate 103. The inlet pipe 110 dischargesexhaust gas into the expansion chamber via opposite end parts in thelongitudinal direction of the expansion chamber, and exhaust gas thathas been discharged into the expansion chamber via the opposite endparts is subjected to a reduction in the sound of the exhaust byexpansion within the expansion chamber.

Two outlet pipes, that is, one outlet pipe 111 and another outlet pipe112, are disposed symmetrically at opposite ends in the longitudinaldirection within the expansion chamber of the silencer main body 101,the one and other outlet pipes 111 and 112 being bent into an S-shape inthe longitudinal direction of the expansion chamber.

The one outlet pipe 111 is supported on the separators 105 and 106 so asto extend therethrough and is formed from a straight upstream-sideoutlet pipe 111 u extending in the longitudinal direction in a frontpart (lower than rear part) in the fore-and-aft direction of thesilencer main body 101, a straight downstream-side outlet pipe 111 dextending in the longitudinal direction in a rear part in thefore-and-aft direction of the silencer main body 1, and an S-shapedintermediate-side outlet pipe 111 n providing communication between theupstream-side and downstream-side outlet pipes 111 u and 111 d. Theupstream end of the upstream-side outlet pipe 111 u is in a central partin the longitudinal direction of the expansion chamber, and abeak-shaped inlet pipe 111 i is connected thereto, the beak-shaped inletpipe 111 i having an opening portion 111 o directed toward the bottom ofthe silencer main body 101.

The other outlet pipe 112 is supported on the separators 107 and 108 soas to extend therethrough, and is formed from a straight upstream-sideoutlet pipe 112 u extending in the longitudinal direction in a frontpart (lower than rear part) in the fore-and-aft direction of thesilencer main body 101, a straight downstream-side outlet pipe 112 dextending in the longitudinal direction in a rear part in thefore-and-aft direction of the silencer main body 1, and an S-shapedintermediate-side outlet pipe 112 n providing communication between theupstream-side and downstream-side outlet pipes 112 u and 112 d. Theupstream end of the upstream-side outlet pipe 112 u is in a central partin the longitudinal direction of the expansion chamber, and atrumpet-shaped inlet pipe 112 i is connected thereto, the trumpet-shapedinlet pipe 112 i having an opening portion 112 o directed in thelongitudinal direction of the silencer main body 101 (a directionsubstantially parallel to the bottom of the silencer main body 101).

As shown in FIGS. 7 to 11, the upstream-side outlet pipe 111 u of theone outlet pipe 111 and the upstream-side outlet pipe 112 u of the otheroutlet pipe 112 are disposed along the bottom within the silencer mainbody 101 so that the distances thereof from the lowest part of thebottom are substantially equal, the inlet pipe 111 i of the one outletpipe 111 and the inlet pipe 112 i of the other outlet pipe 112 u opposeeach other across a predetermined gap, and the opening portion 111 o ofthe one inlet pipe 111 i is directed more toward the bottom side than isthe opening portion 112 o of the other inlet pipe 112 i.

As shown in FIGS. 6, 7, and 10, the downstream end of one outlet pipe111 is supported on the left end plate 103 so as to extend therethroughand is connected to the one tailpipe 113, and the downstream end of theother outlet pipe 112 is supported on the right end plate 104 so as toextend therethrough and is connected to another tailpipe 114. Exhaustgas within the expansion chamber is silenced in the interior of theexpansion chamber and then discharged to the outside from its centralpart through the one outlet pipe 111 and the one tailpipe 113, and theother outlet pipe 112 and the other tailpipe 114.

The operation of the second embodiment is now explained.

Exhaust gas generated by operation of the engine E flows into the inletpipe 110 within the silencer main body 101 from the right-hand side inthe longitudinal direction of the silencer main body 101 through theexhaust introduction pipe 118 via the exhaust pipe Pe. The inlet pipe110 extending in the longitudinal direction within the expansion chamberdischarges exhaust gas into the expansion chamber via the large numberof small holes (punched holes) 122 in its upstream part and the openingat the downstream end. Exhaust gas that has been discharged into theopposite end parts, in the longitudinal direction, of the expansionchamber from the inlet pipe 110 is subjected to a reduction in exhaustsound by expansion in the interior of the expansion chamber and thendischarged to the outside of the silencer main body 101 via two, thatis, the one and other outlet pipes 111 and 112 in the central part ofthe expansion chamber, and the two tailpipes 113 and 114. In this way,exhaust gas enters the expansion chamber from the opposite end parts, inthe longitudinal direction, of the expansion chamber and is dischargedto the outside from the central part of the expansion chamber, and evenwith a long narrow expansion chamber the exhaust sound can be reducedusing the entire expansion chamber.

When the operation of the engine E is stopped and the main silencer MMis cooled, high temperature exhaust gas flowing there is also cooled;moisture contained in the exhaust gas condenses and, as shown in FIGS.8, 9, and 11, becomes condensed water that builds up within the silencermain body 101.

The exhaust silencing device of the second embodiment discharges thecondensed water to the outside via the following process.

[When Condensed Water is at Low Level]

As shown by the solid lines in FIGS. 8, 9, and 11, when the amount ofcondensed water building up at the bottom of the silencer main body 101is small and the water level thereof is low, since the opening portion111 o of the inlet pipe 111 i of the one outlet pipe 111 is directedtoward the bottom of the silencer main body 1, the condensed water isefficiently sucked up through the opening portion 111 o of the oneoutlet pipe 111 and discharged to the outside of the silencer main body1 through the outlet pipe 111.

[When Condensed Water is at High Level]

When the amount of condensed water building up increases and the waterlevel of the condensed water increases from the above state as shown bythe double dotted broken lines in FIGS. 8, 9, and 11, since the openingportion 111 o of the inlet pipe 111 i of the one outlet pipe 111 isdirected toward the bottom of the silencer main body 1, the actualopening area of the opening portion 111 o into which exhaust gas flowsgreatly decreases due to the increase in the water level, the amount ofexhaust gas flowing through the one outlet pipe 111 decreases, and theamount of condensed water discharged from the one outlet pipe 111 alsodecreases accompanying this. In this process, since the extent to whichthe opening portion 112 o of the inlet pipe 112 i of the other outletpipe 112 is directed toward the bottom of the silencer main body 1 issmall or none, the actual opening area of the opening portion 112 o intowhich exhaust gas flows does not decrease a lot even when the waterlevel of condensed water increases, the amount of exhaust gas flowingthrough the other outlet pipe 112 increases by an amount correspondingto the amount by which the exhaust gas flowing through the one outletpipe 111 has decreased, and the flow velocity of the exhaust gas flowingthrough the other outlet pipe 112 increases. This enhances the suctionpower of the other outlet pipe 112 to suck up condensed water, a largeamount of condensed water is sucked into the other outlet pipe 112 anddischarged to the outside of the silencer main body 101, and the waterlevel of the condensed water building up at the bottom of the silencermain body 101 decreases again to the above low level.

Furthermore, since condensed water building up within the silencer mainbody 101 is discharged to the outside from the central part in thelongitudinal direction of the silencer main body 101 via one end or theother end in the longitudinal direction, even with the long narrowsilencer main body 101 it is possible to promptly discharge condensedwater building up there, and it is possible to yet more reliably preventthe effect in reducing exhaust resistance by providing the two outletpipes 111 and 112 from being impaired by condensed water building up.

Embodiments of the present invention are explained above, but thepresent invention is not limited to the embodiments and may be modifiedin a variety of ways within the scope of the present invention.

For example, in the embodiment the exhaust silencing device related tothe present invention is implemented as the main silencer MM, but thismay be implemented as another silencer.

1. An exhaust silencing device comprising a silencer main body (1; 101),an inlet pipe (10; 110) that has at a downstream end thereof an openingportion opening within the silencer main body (1; 101) and that guidesexhaust gas from an engine (E) to the silencer main body (1; 101), andtwo outlet pipes (11, 12; 111, 112) that have at an upstream end thereofan opening portion (11 o, 12 o; 111 o, 112 o) opening within thesilencer main body (1; 101) and that discharge exhaust gas within thesilencer main body (1; 101) to an outside of the silencer main body (1;101), characterized in that the two outlet pipes (11, 12; 111, 112) aredisposed within the silencer main body (1, 101) along a bottom of thesilencer main body (1, 101) so that the distances thereof from thelowest part of said bottom are substantially equal, and the openingportion (11 o; 111 o) of one (11; 111) of the outlet pipes is directedfurther toward the bottom of the silencer main body (1; 101) than is theopening portion (12 o; 112 o) of the other outlet pipe (12; 112).
 2. Theexhaust silencing device according to claim 1, wherein the silencer mainbody (1) is inclined upwardly from an upstream side of the silencer mainbody (1) toward a downstream side of the silencer main body (1) in adirection of flow of exhaust gas, the opening portions (11 o, 12 o) ofsaid one and other outlet pipes (11, 12) are on the upstream side withinthe silencer main body (1), and the opening portion (11 o) of said oneoutlet pipe (11) is inclined downwardly from the upstream side towardthe downstream side.
 3. The exhaust silencing device according to claim1, wherein the two outlet pipes (111, 112) are formed into an S-shapeand are disposed at opposite sides in a longitudinal direction withinthe silencer main body (101), upstream-side outlet pipes (111 u, 112 u)of these outlet pipes (111, 112) are disposed along the bottom of thesilencer main body (101) so that the distances thereof from the lowestpart of said bottom are substantially equal, and the opening portions(111 o, 112 o) formed at the upstream end of said one and other outletpipes (111, 112) are disposed in a central part in the longitudinaldirection of the silencer main body (101).